“Tony Dekker can do a whole lot with just his acoustic guitar and his absolutely stunning voice. That’s all that appeared on a sparsely packaged CDR in 2003 that became the Great Lake Swimmers’ debut album. Over the past 15 years, the band expanded, increased both the tempo and the volume, and by the time of 2015’s “A Forest of Arms,” the band had morphed into a solid roots-rock outfit that didn’t sound all that different from dozens of their peers in Canada, for better or worse.